/*
 * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "gc/shared/barrierSet.hpp"
#include "gc/shenandoah/shenandoahHeap.hpp"
#include "gc/shenandoah/shenandoahHeuristics.hpp"
#include "gc/shenandoah/shenandoahRuntime.hpp"
#include "gc/shenandoah/shenandoahThreadLocalData.hpp"
#include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
#include "gc/shenandoah/c2/shenandoahSupport.hpp"
#include "opto/graphKit.hpp"
#include "opto/idealKit.hpp"
#include "opto/macro.hpp"

ShenandoahBarrierSetC2* ShenandoahBarrierSetC2::bsc2() {
  return reinterpret_cast<ShenandoahBarrierSetC2*>(BarrierSet::barrier_set()->barrier_set_c2());
}

ShenandoahBarrierSetC2State::ShenandoahBarrierSetC2State(Arena* comp_arena)
  : _shenandoah_barriers(new (comp_arena) GrowableArray<ShenandoahWriteBarrierNode*>(comp_arena, 8,  0, NULL)) {
}

int ShenandoahBarrierSetC2State::shenandoah_barriers_count() const {
  return _shenandoah_barriers->length();
}

ShenandoahWriteBarrierNode* ShenandoahBarrierSetC2State::shenandoah_barrier(int idx) const {
  return _shenandoah_barriers->at(idx);
}

void ShenandoahBarrierSetC2State::add_shenandoah_barrier(ShenandoahWriteBarrierNode * n) {
  assert(!_shenandoah_barriers->contains(n), "duplicate entry in barrier list");
  _shenandoah_barriers->append(n);
}

void ShenandoahBarrierSetC2State::remove_shenandoah_barrier(ShenandoahWriteBarrierNode * n) {
  if (_shenandoah_barriers->contains(n)) {
    _shenandoah_barriers->remove(n);
  }
}

#define __ kit->

Node* ShenandoahBarrierSetC2::shenandoah_read_barrier(GraphKit* kit, Node* obj) const {
  if (ShenandoahReadBarrier) {
    obj = shenandoah_read_barrier_impl(kit, obj, false, true, true);
  }
  return obj;
}

Node* ShenandoahBarrierSetC2::shenandoah_storeval_barrier(GraphKit* kit, Node* obj) const {
  if (ShenandoahStoreValEnqueueBarrier) {
    obj = shenandoah_write_barrier(kit, obj);
    obj = shenandoah_enqueue_barrier(kit, obj);
  }
  if (ShenandoahStoreValReadBarrier) {
    obj = shenandoah_read_barrier_impl(kit, obj, true, false, false);
  }
  return obj;
}

Node* ShenandoahBarrierSetC2::shenandoah_read_barrier_impl(GraphKit* kit, Node* obj, bool use_ctrl, bool use_mem, bool allow_fromspace) const {
  const Type* obj_type = obj->bottom_type();
  if (obj_type->higher_equal(TypePtr::NULL_PTR)) {
    return obj;
  }
  const TypePtr* adr_type = ShenandoahBarrierNode::brooks_pointer_type(obj_type);
  Node* mem = use_mem ? __ memory(adr_type) : __ immutable_memory();

  if (! ShenandoahBarrierNode::needs_barrier(&__ gvn(), NULL, obj, mem, allow_fromspace)) {
    // We know it is null, no barrier needed.
    return obj;
  }

  if (obj_type->meet(TypePtr::NULL_PTR) == obj_type->remove_speculative()) {

    // We don't know if it's null or not. Need null-check.
    enum { _not_null_path = 1, _null_path, PATH_LIMIT };
    RegionNode* region = new RegionNode(PATH_LIMIT);
    Node*       phi    = new PhiNode(region, obj_type);
    Node* null_ctrl = __ top();
    Node* not_null_obj = __ null_check_oop(obj, &null_ctrl);

    region->init_req(_null_path, null_ctrl);
    phi   ->init_req(_null_path, __ zerocon(T_OBJECT));

    Node* ctrl = use_ctrl ? __ control() : NULL;
    ShenandoahReadBarrierNode* rb = new ShenandoahReadBarrierNode(ctrl, mem, not_null_obj, allow_fromspace);
    Node* n = __ gvn().transform(rb);

    region->init_req(_not_null_path, __ control());
    phi   ->init_req(_not_null_path, n);

    __ set_control(__ gvn().transform(region));
    __ record_for_igvn(region);
    return __ gvn().transform(phi);

  } else {
    // We know it is not null. Simple barrier is sufficient.
    Node* ctrl = use_ctrl ? __ control() : NULL;
    ShenandoahReadBarrierNode* rb = new ShenandoahReadBarrierNode(ctrl, mem, obj, allow_fromspace);
    Node* n = __ gvn().transform(rb);
    __ record_for_igvn(n);
    return n;
  }
}

Node* ShenandoahBarrierSetC2::shenandoah_write_barrier_helper(GraphKit* kit, Node* obj, const TypePtr* adr_type) const {
  ShenandoahWriteBarrierNode* wb = new ShenandoahWriteBarrierNode(kit->C, kit->control(), kit->memory(adr_type), obj);
  Node* n = __ gvn().transform(wb);
  if (n == wb) { // New barrier needs memory projection.
    Node* proj = __ gvn().transform(new ShenandoahWBMemProjNode(n));
    __ set_memory(proj, adr_type);
  }
  return n;
}

Node* ShenandoahBarrierSetC2::shenandoah_write_barrier(GraphKit* kit, Node* obj) const {
  if (ShenandoahWriteBarrier) {
    obj = shenandoah_write_barrier_impl(kit, obj);
  }
  return obj;
}

Node* ShenandoahBarrierSetC2::shenandoah_write_barrier_impl(GraphKit* kit, Node* obj) const {
  if (! ShenandoahBarrierNode::needs_barrier(&__ gvn(), NULL, obj, NULL, true)) {
    return obj;
  }
  const Type* obj_type = obj->bottom_type();
  const TypePtr* adr_type = ShenandoahBarrierNode::brooks_pointer_type(obj_type);
  Node* n = shenandoah_write_barrier_helper(kit, obj, adr_type);
  __ record_for_igvn(n);
  return n;
}

bool ShenandoahBarrierSetC2::satb_can_remove_pre_barrier(GraphKit* kit, PhaseTransform* phase, Node* adr,
                                                         BasicType bt, uint adr_idx) const {
  intptr_t offset = 0;
  Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
  AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase);

  if (offset == Type::OffsetBot) {
    return false; // cannot unalias unless there are precise offsets
  }

  if (alloc == NULL) {
    return false; // No allocation found
  }

  intptr_t size_in_bytes = type2aelembytes(bt);

  Node* mem = __ memory(adr_idx); // start searching here...

  for (int cnt = 0; cnt < 50; cnt++) {

    if (mem->is_Store()) {

      Node* st_adr = mem->in(MemNode::Address);
      intptr_t st_offset = 0;
      Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);

      if (st_base == NULL) {
        break; // inscrutable pointer
      }

      // Break we have found a store with same base and offset as ours so break
      if (st_base == base && st_offset == offset) {
        break;
      }

      if (st_offset != offset && st_offset != Type::OffsetBot) {
        const int MAX_STORE = BytesPerLong;
        if (st_offset >= offset + size_in_bytes ||
            st_offset <= offset - MAX_STORE ||
            st_offset <= offset - mem->as_Store()->memory_size()) {
          // Success:  The offsets are provably independent.
          // (You may ask, why not just test st_offset != offset and be done?
          // The answer is that stores of different sizes can co-exist
          // in the same sequence of RawMem effects.  We sometimes initialize
          // a whole 'tile' of array elements with a single jint or jlong.)
          mem = mem->in(MemNode::Memory);
          continue; // advance through independent store memory
        }
      }

      if (st_base != base
          && MemNode::detect_ptr_independence(base, alloc, st_base,
                                              AllocateNode::Ideal_allocation(st_base, phase),
                                              phase)) {
        // Success:  The bases are provably independent.
        mem = mem->in(MemNode::Memory);
        continue; // advance through independent store memory
      }
    } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {

      InitializeNode* st_init = mem->in(0)->as_Initialize();
      AllocateNode* st_alloc = st_init->allocation();

      // Make sure that we are looking at the same allocation site.
      // The alloc variable is guaranteed to not be null here from earlier check.
      if (alloc == st_alloc) {
        // Check that the initialization is storing NULL so that no previous store
        // has been moved up and directly write a reference
        Node* captured_store = st_init->find_captured_store(offset,
                                                            type2aelembytes(T_OBJECT),
                                                            phase);
        if (captured_store == NULL || captured_store == st_init->zero_memory()) {
          return true;
        }
      }
    }

    // Unless there is an explicit 'continue', we must bail out here,
    // because 'mem' is an inscrutable memory state (e.g., a call).
    break;
  }

  return false;
}

#undef __
#define __ ideal.

void ShenandoahBarrierSetC2::satb_write_barrier_pre(GraphKit* kit,
                                                    bool do_load,
                                                    Node* obj,
                                                    Node* adr,
                                                    uint alias_idx,
                                                    Node* val,
                                                    const TypeOopPtr* val_type,
                                                    Node* pre_val,
                                                    BasicType bt) const {
  // Some sanity checks
  // Note: val is unused in this routine.

  if (do_load) {
    // We need to generate the load of the previous value
    assert(obj != NULL, "must have a base");
    assert(adr != NULL, "where are loading from?");
    assert(pre_val == NULL, "loaded already?");
    assert(val_type != NULL, "need a type");

    if (ReduceInitialCardMarks
        && satb_can_remove_pre_barrier(kit, &kit->gvn(), adr, bt, alias_idx)) {
      return;
    }

  } else {
    // In this case both val_type and alias_idx are unused.
    assert(pre_val != NULL, "must be loaded already");
    // Nothing to be done if pre_val is null.
    if (pre_val->bottom_type() == TypePtr::NULL_PTR) return;
    assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here");
  }
  assert(bt == T_OBJECT, "or we shouldn't be here");

  IdealKit ideal(kit, true);

  Node* tls = __ thread(); // ThreadLocalStorage

  Node* no_base = __ top();
  Node* zero  = __ ConI(0);
  Node* zeroX = __ ConX(0);

  float likely  = PROB_LIKELY(0.999);
  float unlikely  = PROB_UNLIKELY(0.999);

  // Offsets into the thread
  const int index_offset   = in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset());
  const int buffer_offset  = in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset());

  // Now the actual pointers into the thread
  Node* buffer_adr  = __ AddP(no_base, tls, __ ConX(buffer_offset));
  Node* index_adr   = __ AddP(no_base, tls, __ ConX(index_offset));

  // Now some of the values
  Node* marking;
  Node* gc_state = __ AddP(no_base, tls, __ ConX(in_bytes(ShenandoahThreadLocalData::gc_state_offset())));
  Node* ld = __ load(__ ctrl(), gc_state, TypeInt::BYTE, T_BYTE, Compile::AliasIdxRaw);
  marking = __ AndI(ld, __ ConI(ShenandoahHeap::MARKING));
  assert(ShenandoahWriteBarrierNode::is_gc_state_load(ld), "Should match the shape");

  // if (!marking)
  __ if_then(marking, BoolTest::ne, zero, unlikely); {
    BasicType index_bt = TypeX_X->basic_type();
    assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 SATBMarkQueue::_index with wrong size.");
    Node* index   = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw);

    if (do_load) {
      // load original value
      // alias_idx correct??
      pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx);
    }

    // if (pre_val != NULL)
    __ if_then(pre_val, BoolTest::ne, kit->null()); {
      Node* buffer  = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw);

      // is the queue for this thread full?
      __ if_then(index, BoolTest::ne, zeroX, likely); {

        // decrement the index
        Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t))));

        // Now get the buffer location we will log the previous value into and store it
        Node *log_addr = __ AddP(no_base, buffer, next_index);
        __ store(__ ctrl(), log_addr, pre_val, T_OBJECT, Compile::AliasIdxRaw, MemNode::unordered);
        // update the index
        __ store(__ ctrl(), index_adr, next_index, index_bt, Compile::AliasIdxRaw, MemNode::unordered);

      } __ else_(); {

        // logging buffer is full, call the runtime
        const TypeFunc *tf = ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type();
        __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), "shenandoah_wb_pre", pre_val, tls);
      } __ end_if();  // (!index)
    } __ end_if();  // (pre_val != NULL)
  } __ end_if();  // (!marking)

  // Final sync IdealKit and GraphKit.
  kit->final_sync(ideal);

  if (ShenandoahSATBBarrier && adr != NULL) {
    Node* c = kit->control();
    Node* call = c->in(1)->in(1)->in(1)->in(0);
    assert(is_shenandoah_wb_pre_call(call), "shenandoah_wb_pre call expected");
    call->add_req(adr);
  }
}

bool ShenandoahBarrierSetC2::is_shenandoah_wb_pre_call(Node* call) {
  return call->is_CallLeaf() &&
         call->as_CallLeaf()->entry_point() == CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry);
}

bool ShenandoahBarrierSetC2::is_shenandoah_marking_if(PhaseTransform *phase, Node* n) {
  if (n->Opcode() != Op_If) {
    return false;
  }

  Node* bol = n->in(1);
  assert(bol->is_Bool(), "");
  Node* cmpx = bol->in(1);
  if (bol->as_Bool()->_test._test == BoolTest::ne &&
      cmpx->is_Cmp() && cmpx->in(2) == phase->intcon(0) &&
      is_shenandoah_state_load(cmpx->in(1)->in(1)) &&
      cmpx->in(1)->in(2)->is_Con() &&
      cmpx->in(1)->in(2) == phase->intcon(ShenandoahHeap::MARKING)) {
    return true;
  }

  return false;
}

bool ShenandoahBarrierSetC2::is_shenandoah_state_load(Node* n) {
  if (!n->is_Load()) return false;
  const int state_offset = in_bytes(ShenandoahThreadLocalData::gc_state_offset());
  return n->in(2)->is_AddP() && n->in(2)->in(2)->Opcode() == Op_ThreadLocal
         && n->in(2)->in(3)->is_Con()
         && n->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == state_offset;
}

void ShenandoahBarrierSetC2::shenandoah_write_barrier_pre(GraphKit* kit,
                                                          bool do_load,
                                                          Node* obj,
                                                          Node* adr,
                                                          uint alias_idx,
                                                          Node* val,
                                                          const TypeOopPtr* val_type,
                                                          Node* pre_val,
                                                          BasicType bt) const {
  if (ShenandoahSATBBarrier) {
    IdealKit ideal(kit);
    kit->sync_kit(ideal);

    satb_write_barrier_pre(kit, do_load, obj, adr, alias_idx, val, val_type, pre_val, bt);

    ideal.sync_kit(kit);
    kit->final_sync(ideal);
  }
}

Node* ShenandoahBarrierSetC2::shenandoah_enqueue_barrier(GraphKit* kit, Node* pre_val) const {
  return kit->gvn().transform(new ShenandoahEnqueueBarrierNode(pre_val));
}

// Helper that guards and inserts a pre-barrier.
void ShenandoahBarrierSetC2::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset,
                                                Node* pre_val, bool need_mem_bar) const {
  // We could be accessing the referent field of a reference object. If so, when G1
  // is enabled, we need to log the value in the referent field in an SATB buffer.
  // This routine performs some compile time filters and generates suitable
  // runtime filters that guard the pre-barrier code.
  // Also add memory barrier for non volatile load from the referent field
  // to prevent commoning of loads across safepoint.

  // Some compile time checks.

  // If offset is a constant, is it java_lang_ref_Reference::_reference_offset?
  const TypeX* otype = offset->find_intptr_t_type();
  if (otype != NULL && otype->is_con() &&
      otype->get_con() != java_lang_ref_Reference::referent_offset) {
    // Constant offset but not the reference_offset so just return
    return;
  }

  // We only need to generate the runtime guards for instances.
  const TypeOopPtr* btype = base_oop->bottom_type()->isa_oopptr();
  if (btype != NULL) {
    if (btype->isa_aryptr()) {
      // Array type so nothing to do
      return;
    }

    const TypeInstPtr* itype = btype->isa_instptr();
    if (itype != NULL) {
      // Can the klass of base_oop be statically determined to be
      // _not_ a sub-class of Reference and _not_ Object?
      ciKlass* klass = itype->klass();
      if ( klass->is_loaded() &&
          !klass->is_subtype_of(kit->env()->Reference_klass()) &&
          !kit->env()->Object_klass()->is_subtype_of(klass)) {
        return;
      }
    }
  }

  // The compile time filters did not reject base_oop/offset so
  // we need to generate the following runtime filters
  //
  // if (offset == java_lang_ref_Reference::_reference_offset) {
  //   if (instance_of(base, java.lang.ref.Reference)) {
  //     pre_barrier(_, pre_val, ...);
  //   }
  // }

  float likely   = PROB_LIKELY(  0.999);
  float unlikely = PROB_UNLIKELY(0.999);

  IdealKit ideal(kit);

  Node* referent_off = __ ConX(java_lang_ref_Reference::referent_offset);

  __ if_then(offset, BoolTest::eq, referent_off, unlikely); {
      // Update graphKit memory and control from IdealKit.
      kit->sync_kit(ideal);

      Node* ref_klass_con = kit->makecon(TypeKlassPtr::make(kit->env()->Reference_klass()));
      Node* is_instof = kit->gen_instanceof(base_oop, ref_klass_con);

      // Update IdealKit memory and control from graphKit.
      __ sync_kit(kit);

      Node* one = __ ConI(1);
      // is_instof == 0 if base_oop == NULL
      __ if_then(is_instof, BoolTest::eq, one, unlikely); {

        // Update graphKit from IdeakKit.
        kit->sync_kit(ideal);

        // Use the pre-barrier to record the value in the referent field
        satb_write_barrier_pre(kit, false /* do_load */,
                               NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
                               pre_val /* pre_val */,
                               T_OBJECT);
        if (need_mem_bar) {
          // Add memory barrier to prevent commoning reads from this field
          // across safepoint since GC can change its value.
          kit->insert_mem_bar(Op_MemBarCPUOrder);
        }
        // Update IdealKit from graphKit.
        __ sync_kit(kit);

      } __ end_if(); // _ref_type != ref_none
  } __ end_if(); // offset == referent_offset

  // Final sync IdealKit and GraphKit.
  kit->final_sync(ideal);
}

#undef __

const TypeFunc* ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type() {
  const Type **fields = TypeTuple::fields(2);
  fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
  fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread
  const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields);

  // create result type (range)
  fields = TypeTuple::fields(0);
  const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields);

  return TypeFunc::make(domain, range);
}

const TypeFunc* ShenandoahBarrierSetC2::shenandoah_clone_barrier_Type() {
  const Type **fields = TypeTuple::fields(1);
  fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
  const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+1, fields);

  // create result type (range)
  fields = TypeTuple::fields(0);
  const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields);

  return TypeFunc::make(domain, range);
}

const TypeFunc* ShenandoahBarrierSetC2::shenandoah_write_barrier_Type() {
  const Type **fields = TypeTuple::fields(1);
  fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
  const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+1, fields);

  // create result type (range)
  fields = TypeTuple::fields(1);
  fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL;
  const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+1, fields);

  return TypeFunc::make(domain, range);
}

Node* ShenandoahBarrierSetC2::store_at(C2Access& access, C2AccessValue& val) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::store_at(access, val);
}

Node* ShenandoahBarrierSetC2::store_at_resolved(C2Access& access, C2AccessValue& val) const {
  DecoratorSet decorators = access.decorators();
  GraphKit* kit = access.kit();

  const TypePtr* adr_type = access.addr().type();
  Node* adr = access.addr().node();

  bool anonymous = (decorators & ON_UNKNOWN_OOP_REF) != 0;
  bool on_heap = (decorators & IN_HEAP) != 0;

  if (!access.is_oop() || (!on_heap && !anonymous)) {
    return BarrierSetC2::store_at_resolved(access, val);
  }

  uint adr_idx = kit->C->get_alias_index(adr_type);
  assert(adr_idx != Compile::AliasIdxTop, "use other store_to_memory factory" );
  Node* value = val.node();
  value = shenandoah_storeval_barrier(kit, value);
  val.set_node(value);
  shenandoah_write_barrier_pre(kit, true /* do_load */, /*kit->control(),*/ access.base(), adr, adr_idx, val.node(),
              static_cast<const TypeOopPtr*>(val.type()), NULL /* pre_val */, access.type());
  return BarrierSetC2::store_at_resolved(access, val);
}

Node* ShenandoahBarrierSetC2::load_at(C2Access& access, const Type* val_type) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::load_at(access, val_type);
}

Node* ShenandoahBarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const {
  DecoratorSet decorators = access.decorators();
  GraphKit* kit = access.kit();

  Node* adr = access.addr().node();
  Node* obj = access.base();

  bool mismatched = (decorators & C2_MISMATCHED) != 0;
  bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
  bool on_heap = (decorators & IN_HEAP) != 0;
  bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0;
  bool is_unordered = (decorators & MO_UNORDERED) != 0;
  bool need_cpu_mem_bar = !is_unordered || mismatched || !on_heap;

  Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : kit->top();
  Node* load = BarrierSetC2::load_at_resolved(access, val_type);

  // If we are reading the value of the referent field of a Reference
  // object (either by using Unsafe directly or through reflection)
  // then, if SATB is enabled, we need to record the referent in an
  // SATB log buffer using the pre-barrier mechanism.
  // Also we need to add memory barrier to prevent commoning reads
  // from this field across safepoint since GC can change its value.
  bool need_read_barrier = ShenandoahKeepAliveBarrier &&
    (on_heap && (on_weak || (unknown && offset != kit->top() && obj != kit->top())));

  if (!access.is_oop() || !need_read_barrier) {
    return load;
  }

  if (on_weak) {
    // Use the pre-barrier to record the value in the referent field
    satb_write_barrier_pre(kit, false /* do_load */,
                           NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
                           load /* pre_val */, T_OBJECT);
    // Add memory barrier to prevent commoning reads from this field
    // across safepoint since GC can change its value.
    kit->insert_mem_bar(Op_MemBarCPUOrder);
  } else if (unknown) {
    // We do not require a mem bar inside pre_barrier if need_mem_bar
    // is set: the barriers would be emitted by us.
    insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar);
  }

  return load;
}

Node* ShenandoahBarrierSetC2::atomic_cmpxchg_val_at_resolved(C2AtomicAccess& access, Node* expected_val,
                                                   Node* val, const Type* value_type) const {
  GraphKit* kit = access.kit();
  if (access.is_oop()) {
    val = shenandoah_storeval_barrier(kit, val);
    shenandoah_write_barrier_pre(kit, false /* do_load */,
                                 NULL, NULL, max_juint, NULL, NULL,
                                 expected_val /* pre_val */, T_OBJECT);

  }
  return BarrierSetC2::atomic_cmpxchg_val_at_resolved(access, expected_val, val, value_type);
}

Node* ShenandoahBarrierSetC2::atomic_cmpxchg_val_at(C2AtomicAccess& access, Node* expected_val,
                                                    Node* new_val, const Type* val_type) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::atomic_cmpxchg_val_at(access, expected_val, new_val, val_type);
}

Node* ShenandoahBarrierSetC2::atomic_cmpxchg_bool_at_resolved(C2AtomicAccess& access, Node* expected_val,
                                                              Node* val, const Type* value_type) const {
  GraphKit* kit = access.kit();
  if (access.is_oop()) {
    val = shenandoah_storeval_barrier(kit, val);
    shenandoah_write_barrier_pre(kit, false /* do_load */,
                                 NULL, NULL, max_juint, NULL, NULL,
                                 expected_val /* pre_val */, T_OBJECT);
  }
  return BarrierSetC2::atomic_cmpxchg_bool_at_resolved(access, expected_val, val, value_type);
}

Node* ShenandoahBarrierSetC2::atomic_cmpxchg_bool_at(C2AtomicAccess& access, Node* expected_val,
                                                     Node* new_val, const Type* val_type) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::atomic_cmpxchg_bool_at(access, expected_val, new_val, val_type);
}

Node* ShenandoahBarrierSetC2::atomic_xchg_at_resolved(C2AtomicAccess& access, Node* val, const Type* value_type) const {
  GraphKit* kit = access.kit();
  if (access.is_oop()) {
    val = shenandoah_storeval_barrier(kit, val);
  }
  Node* result = BarrierSetC2::atomic_xchg_at_resolved(access, val, value_type);
  if (access.is_oop()) {
    shenandoah_write_barrier_pre(kit, false /* do_load */,
                                 NULL, NULL, max_juint, NULL, NULL,
                                 result /* pre_val */, T_OBJECT);
  }
  return result;
}

Node* ShenandoahBarrierSetC2::atomic_xchg_at(C2AtomicAccess& access, Node* new_val, const Type* value_type) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::atomic_xchg_at(access, new_val, value_type);
}

Node* ShenandoahBarrierSetC2::atomic_add_at(C2AtomicAccess& access, Node* new_val, const Type* value_type) const {
  // TODO: Implement using proper barriers.
  return BarrierSetC2::atomic_add_at(access, new_val, value_type);
}

void ShenandoahBarrierSetC2::clone(GraphKit* kit, Node* src, Node* dst, Node* size, bool is_array) const {
  // TODO: Implement using proper barriers.
  BarrierSetC2::clone(kit, src, dst, size, is_array);
}

Node* ShenandoahBarrierSetC2::resolve_for_read(GraphKit* kit, Node* n) const {
  return shenandoah_read_barrier(kit, n);
}

Node* ShenandoahBarrierSetC2::resolve_for_write(GraphKit* kit, Node* n) const {
  return shenandoah_write_barrier(kit, n);
}

// Support for GC barriers emitted during parsing
bool ShenandoahBarrierSetC2::is_gc_barrier_node(Node* node) const {
  if (node->Opcode() != Op_CallLeaf && node->Opcode() != Op_CallLeafNoFP) {
    return false;
  }
  CallLeafNode *call = node->as_CallLeaf();
  if (call->_name == NULL) {
    return false;
  }

  return strcmp(call->_name, "shenandoah_clone_barrier") == 0 ||
         strcmp(call->_name, "shenandoah_cas_obj") == 0 ||
         strcmp(call->_name, "shenandoah_wb_pre") == 0;
}

Node* ShenandoahBarrierSetC2::step_over_gc_barrier(Node* c) const {
  return ShenandoahBarrierNode::skip_through_barrier(c);
}

bool ShenandoahBarrierSetC2::array_copy_requires_gc_barriers(BasicType type) const {
  return false;
}

// Support for macro expanded GC barriers
void ShenandoahBarrierSetC2::register_potential_barrier_node(Node* node) const {
  if (node->Opcode() == Op_ShenandoahWriteBarrier) {
    state()->add_shenandoah_barrier((ShenandoahWriteBarrierNode*) node);
  }
}

void ShenandoahBarrierSetC2::unregister_potential_barrier_node(Node* node) const {
  if (node->Opcode() == Op_ShenandoahWriteBarrier) {
    state()->remove_shenandoah_barrier((ShenandoahWriteBarrierNode*) node);
  }
}

void ShenandoahBarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* n) const {
  if (is_shenandoah_wb_pre_call(n)) {
    shenandoah_eliminate_wb_pre(n, &macro->igvn());
  }
}

void ShenandoahBarrierSetC2::shenandoah_eliminate_wb_pre(Node* call, PhaseIterGVN* igvn) const {
  assert(UseShenandoahGC && is_shenandoah_wb_pre_call(call), "");
  Node* c = call->as_Call()->proj_out(TypeFunc::Control);
  c = c->unique_ctrl_out();
  assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
  c = c->unique_ctrl_out();
  assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
  Node* iff = c->in(1)->is_IfProj() ? c->in(1)->in(0) : c->in(2)->in(0);
  assert(iff->is_If(), "expect test");
  if (!is_shenandoah_marking_if(igvn, iff)) {
    c = c->unique_ctrl_out();
    assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
    iff = c->in(1)->is_IfProj() ? c->in(1)->in(0) : c->in(2)->in(0);
    assert(is_shenandoah_marking_if(igvn, iff), "expect marking test");
  }
  Node* cmpx = iff->in(1)->in(1);
  igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
  igvn->rehash_node_delayed(call);
  call->del_req(call->req()-1);
}

void ShenandoahBarrierSetC2::enqueue_useful_gc_barrier(Unique_Node_List &worklist, Node* node) const {
}

void ShenandoahBarrierSetC2::eliminate_useless_gc_barriers(Unique_Node_List &useful) const {
  for (int i = state()->shenandoah_barriers_count()-1; i >= 0; i--) {
    ShenandoahWriteBarrierNode* n = state()->shenandoah_barrier(i);
    if (!useful.member(n)) {
      state()->remove_shenandoah_barrier(n);
    }
  }

}

void ShenandoahBarrierSetC2::add_users_to_worklist(Unique_Node_List* worklist) const {}

void* ShenandoahBarrierSetC2::create_barrier_state(Arena* comp_arena) const {
  return new(comp_arena) ShenandoahBarrierSetC2State(comp_arena);
}

ShenandoahBarrierSetC2State* ShenandoahBarrierSetC2::state() const {
  return reinterpret_cast<ShenandoahBarrierSetC2State*>(Compile::current()->barrier_set_state());
}

// If the BarrierSetC2 state has kept macro nodes in its compilation unit state to be
// expanded later, then now is the time to do so.
bool ShenandoahBarrierSetC2::expand_macro_nodes(PhaseMacroExpand* macro) const { return false; }
void ShenandoahBarrierSetC2::verify_gc_barriers(bool post_parse) const {
#ifdef ASSERT
  if (ShenandoahVerifyOptoBarriers && !post_parse) {
    ShenandoahBarrierNode::verify(Compile::current()->root());
  }
#endif
}

Node* ShenandoahBarrierSetC2::ideal_node(PhaseGVN *phase, Node* n, bool can_reshape) const {
  if (is_shenandoah_wb_pre_call(n)) {
    uint cnt = ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type()->domain()->cnt();
    if (n->req() > cnt) {
      Node* addp = n->in(cnt);
      if (has_only_shenandoah_wb_pre_uses(addp)) {
        n->del_req(cnt);
        if (can_reshape) {
          phase->is_IterGVN()->_worklist.push(addp);
        }
        return n;
      }
    }
  }
  return NULL;
}

bool ShenandoahBarrierSetC2::has_only_shenandoah_wb_pre_uses(Node* n) {
  if (!UseShenandoahGC) {
    return false;
  }
  for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
    Node* u = n->fast_out(i);
    if (!is_shenandoah_wb_pre_call(u)) {
      return false;
    }
  }
  return n->outcnt() > 0;
}